“Earlier, media had reported that a Kazakh citizen, Aryshev Maksim, born in 1996, was allegedly involved in the blast. I want to say that this information is not true,” Nurgali Bilisbekov of Kazakhstan’s National Security Committee said.

The explosion occurred as the train was traveling between the Tekhnologichesky Institut and Sennaya Ploshchad stations. At least 14 people were killed and 51 injured, according to the latest data.

All possible causes are being considered, including terrorism, Russian President Vladimir Putin said on Monday following the incident.

“Certainly, we will consider all variants, common, criminal, first of all, of a terrorist nature,” he said.

Russia’s Investigative Committee has launched a probe to determine whether the blast was a terrorist act.